ps and wall; How do they work?

[Marc Unangst]

gwyn at smoke.BRL.MIL (Doug Gwyn) writes:
> Any version of "wall" that writes on terminals that have had "mesg n"
> executed on them is BROKEN.  You can fix that by removing /bin/wall.

I disagree.  When you're shutting the system down, it's definitely a
good idea to let the other people on it know at least a few minutes in
advance about the shutdown.  If they have write perms turned off and
/bin/wall won't tell them about it, how do you notify them?  Phone
each of them individually?  Manually echo(1) a message to their
terminal?

If /bin/wall is sending messages to depermitted terminals when the
user isn't the superuser, that's different.  But just like with
write(1), the superuser should be able to send messages even to users
who have done a "mesg n".

Better yet, since the ordinary user has little or no use for wall(1),
just move /bin/wall to /etc/wall and permit it 700.

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